patch 8.2.4042: Vim9: build error

Problem:    Vim9: build error.
Solution:   Use grow array instead of character pointer.
diff --git a/src/version.c b/src/version.c
index 27512d4..579718e 100644
--- a/src/version.c
+++ b/src/version.c
@@ -751,6 +751,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    4042,
+/**/
     4041,
 /**/
     4040,
diff --git a/src/vim9execute.c b/src/vim9execute.c
index 63c07fe..5fab27d 100644
--- a/src/vim9execute.c
+++ b/src/vim9execute.c
@@ -3344,13 +3344,14 @@
 		    list_functions(NULL);
 		else
 		{
-		    exarg_T ea;
-		    char_u  *line_to_free = NULL;
+		    exarg_T	ea;
+		    garray_T	lines_to_free;
 
 		    CLEAR_FIELD(ea);
 		    ea.cmd = ea.arg = iptr->isn_arg.string;
-		    define_function(&ea, NULL, &line_to_free);
-		    vim_free(line_to_free);
+		    ga_init2(&lines_to_free, sizeof(char_u *), 50);
+		    define_function(&ea, NULL, &lines_to_free);
+		    ga_clear_strings(&lines_to_free);
 		}
 		break;